// SPDX-License-Identifier: MIT OR Apache-2.0

use cosmic_text::{
    Action, Attrs, Buffer, Edit, Family, FontSystem, Metrics, Motion, SwashCache, SyntaxEditor,
    SyntaxSystem,
};
use std::{env, fs, num::NonZeroU32, rc::Rc, slice};
use tiny_skia::{Paint, PixmapMut, Rect, Transform};
use winit::{
    dpi::{PhysicalPosition, PhysicalSize},
    event::{ElementState, Event, KeyEvent, MouseButton, MouseScrollDelta, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    keyboard::{Key, NamedKey},
    window::WindowBuilder,
};

fn main() {
    env_logger::init();

    let path = env::args().nth(1).unwrap_or_default();

    let event_loop = EventLoop::new().unwrap();
    let window = Rc::new(WindowBuilder::new().build(&event_loop).unwrap());
    let context = softbuffer::Context::new(window.clone()).unwrap();
    let mut surface = softbuffer::Surface::new(&context, window.clone()).unwrap();
    let mut font_system = FontSystem::new();
    let syntax_system = SyntaxSystem::new();
    let mut swash_cache = SwashCache::new();

    let mut display_scale = window.scale_factor() as f32;

    let scrollbar_width = 12.0;
    let font_sizes = [
        Metrics::new(10.0, 14.0), // Caption
        Metrics::new(14.0, 20.0), // Body
        Metrics::new(20.0, 28.0), // Title 4
        Metrics::new(24.0, 32.0), // Title 3
        Metrics::new(28.0, 36.0), // Title 2
        Metrics::new(32.0, 44.0), // Title 1
    ];
    let font_size_default = 1; // Body
    let mut font_size_i = font_size_default;

    let mut editor = SyntaxEditor::new(
        Buffer::new(
            &mut font_system,
            font_sizes[font_size_i].scale(display_scale),
        ),
        &syntax_system,
        "base16-eighties.dark",
    )
    .unwrap();
    let mut editor = editor.borrow_with(&mut font_system);

    let attrs = Attrs::new().family(Family::Monospace);

    match editor.load_text(&path, attrs) {
        Ok(()) => (),
        Err(err) => {
            log::error!("failed to load {:?}: {}", path, err);
        }
    }

    let mut ctrl_pressed = false;
    let mut mouse_x = 0.0;
    let mut mouse_y = 0.0;
    let mut mouse_left = ElementState::Released;

    event_loop
        .run(|event, elwt| {
            elwt.set_control_flow(ControlFlow::Wait);

            let Event::WindowEvent { window_id, event } = event else {
                return;
            };

            match event {
                WindowEvent::ScaleFactorChanged { scale_factor, .. } => {
                    log::info!("Updated scale factor for {window_id:?}");

                    display_scale = scale_factor as f32;
                    editor.with_buffer_mut(|buffer| {
                        buffer.set_metrics(font_sizes[font_size_i].scale(display_scale))
                    });

                    window.request_redraw();
                }
                WindowEvent::RedrawRequested => {
                    let (width, height) = {
                        let size = window.inner_size();
                        (size.width, size.height)
                    };

                    surface
                        .resize(
                            NonZeroU32::new(width).unwrap(),
                            NonZeroU32::new(height).unwrap(),
                        )
                        .unwrap();

                    let mut surface_buffer = surface.buffer_mut().unwrap();
                    let surface_buffer_u8 = unsafe {
                        slice::from_raw_parts_mut(
                            surface_buffer.as_mut_ptr() as *mut u8,
                            surface_buffer.len() * 4,
                        )
                    };
                    let mut pixmap =
                        PixmapMut::from_bytes(surface_buffer_u8, width, height).unwrap();
                    pixmap.fill(tiny_skia::Color::from_rgba8(0, 0, 0, 0xFF));

                    editor.with_buffer_mut(|buffer| {
                        buffer.set_size(
                            Some(width as f32 - scrollbar_width * display_scale),
                            Some(height as f32),
                        )
                    });

                    let mut paint = Paint {
                        anti_alias: false,
                        ..Default::default()
                    };
                    editor.shape_as_needed(true);
                    editor.draw(&mut swash_cache, |x, y, w, h, color| {
                        // Note: due to softbuffer and tiny_skia having incompatible internal color representations we swap
                        // the red and blue channels here
                        paint.set_color_rgba8(color.b(), color.g(), color.r(), color.a());
                        pixmap.fill_rect(
                            Rect::from_xywh(x as f32, y as f32, w as f32, h as f32).unwrap(),
                            &paint,
                            Transform::identity(),
                            None,
                        );
                    });
                    if let Some((x, y)) = editor.cursor_position() {
                        window.set_ime_cursor_area(
                            PhysicalPosition::new(x, y),
                            PhysicalSize::new(20, 20),
                        );
                    }

                    // Draw scrollbar
                    {
                        let mut start_line_opt = None;
                        let mut end_line = 0;
                        editor.with_buffer(|buffer| {
                            for run in buffer.layout_runs() {
                                end_line = run.line_i;
                                if start_line_opt.is_none() {
                                    start_line_opt = Some(end_line);
                                }
                            }
                        });

                        let start_line = start_line_opt.unwrap_or(end_line);
                        let lines = editor.with_buffer(|buffer| buffer.lines.len());
                        let start_y = (start_line * height as usize) / lines;
                        let end_y = (end_line * height as usize) / lines;
                        paint.set_color_rgba8(0xFF, 0xFF, 0xFF, 0x40);
                        if end_y > start_y {
                            pixmap.fill_rect(
                                Rect::from_xywh(
                                    width as f32 - scrollbar_width * display_scale,
                                    start_y as f32,
                                    scrollbar_width * display_scale,
                                    (end_y - start_y) as f32,
                                )
                                .unwrap(),
                                &paint,
                                Transform::identity(),
                                None,
                            );
                        }
                    }

                    surface_buffer.present().unwrap();
                }
                WindowEvent::ModifiersChanged(modifiers) => {
                    ctrl_pressed = modifiers.state().control_key()
                }
                WindowEvent::KeyboardInput { event, .. } => {
                    let KeyEvent {
                        logical_key, state, ..
                    } = event;

                    if state.is_pressed() {
                        match logical_key {
                            Key::Named(NamedKey::ArrowLeft) => {
                                editor.action(Action::Motion(Motion::Left))
                            }
                            Key::Named(NamedKey::ArrowRight) => {
                                editor.action(Action::Motion(Motion::Right))
                            }
                            Key::Named(NamedKey::ArrowUp) => {
                                editor.action(Action::Motion(Motion::Up))
                            }
                            Key::Named(NamedKey::ArrowDown) => {
                                editor.action(Action::Motion(Motion::Down))
                            }
                            Key::Named(NamedKey::Home) => {
                                editor.action(Action::Motion(Motion::Home))
                            }
                            Key::Named(NamedKey::End) => editor.action(Action::Motion(Motion::End)),
                            Key::Named(NamedKey::PageUp) => {
                                editor.action(Action::Motion(Motion::PageUp))
                            }
                            Key::Named(NamedKey::PageDown) => {
                                editor.action(Action::Motion(Motion::PageDown))
                            }
                            Key::Named(NamedKey::Escape) => editor.action(Action::Escape),
                            Key::Named(NamedKey::Enter) => editor.action(Action::Enter),
                            Key::Named(NamedKey::Backspace) => editor.action(Action::Backspace),
                            Key::Named(NamedKey::Delete) => editor.action(Action::Delete),
                            Key::Named(key) => {
                                if let Some(text) = key.to_text() {
                                    for c in text.chars() {
                                        editor.action(Action::Insert(c));
                                    }
                                }
                            }
                            Key::Character(text) => {
                                if ctrl_pressed {
                                    match &*text {
                                        "0" => {
                                            font_size_i = font_size_default;
                                            editor.with_buffer_mut(|buffer| {
                                                buffer.set_metrics(
                                                    font_sizes[font_size_i].scale(display_scale),
                                                )
                                            });
                                        }
                                        "-" => {
                                            if font_size_i > 0 {
                                                font_size_i -= 1;
                                                editor.with_buffer_mut(|buffer| {
                                                    buffer.set_metrics(
                                                        font_sizes[font_size_i]
                                                            .scale(display_scale),
                                                    )
                                                });
                                            }
                                        }
                                        "=" => {
                                            if font_size_i + 1 < font_sizes.len() {
                                                font_size_i += 1;
                                                editor.with_buffer_mut(|buffer| {
                                                    buffer.set_metrics(
                                                        font_sizes[font_size_i]
                                                            .scale(display_scale),
                                                    )
                                                });
                                            }
                                        }
                                        "s" => {
                                            let mut text = String::new();
                                            editor.with_buffer(|buffer| {
                                                for line in buffer.lines.iter() {
                                                    text.push_str(line.text());
                                                    text.push_str(line.ending().as_str());
                                                }
                                            });
                                            fs::write(&path, &text).unwrap();
                                            log::info!("saved {:?}", path);
                                        }
                                        _ => {}
                                    }
                                } else {
                                    for c in text.chars() {
                                        editor.action(Action::Insert(c));
                                    }
                                }
                            }
                            _ => {}
                        }
                        window.request_redraw();
                    }
                }
                WindowEvent::CursorMoved {
                    device_id: _,
                    position,
                } => {
                    // Update saved mouse position for use when handling click events
                    mouse_x = position.x;
                    mouse_y = position.y;

                    // Implement dragging
                    if mouse_left.is_pressed() {
                        // Execute Drag editor action (update selection)
                        editor.action(Action::Drag {
                            x: position.x as i32,
                            y: position.y as i32,
                        });

                        // Scroll if cursor is near edge of window while dragging
                        if mouse_y <= 5.0 {
                            editor.action(Action::Scroll { pixels: -20.0 });
                        } else if mouse_y - 5.0 >= window.inner_size().height as f64 {
                            editor.action(Action::Scroll { pixels: 20.0 });
                        }

                        window.request_redraw();
                    }
                }
                WindowEvent::MouseInput {
                    device_id: _,
                    state,
                    button,
                } => {
                    if button == MouseButton::Left {
                        if state == ElementState::Pressed && mouse_left == ElementState::Released {
                            editor.action(Action::Click {
                                x: mouse_x as i32,
                                y: mouse_y as i32,
                            });
                            window.request_redraw();
                        }
                        mouse_left = state;
                    }
                }
                WindowEvent::MouseWheel {
                    device_id: _,
                    delta,
                    phase: _,
                } => {
                    let pixel_delta = match delta {
                        MouseScrollDelta::LineDelta(_x, y) => y * 20.0,
                        MouseScrollDelta::PixelDelta(PhysicalPosition { x: _, y }) => y as f32,
                    };
                    if pixel_delta != 0.0 {
                        editor.action(Action::Scroll {
                            pixels: -pixel_delta,
                        });
                    }
                    window.request_redraw();
                }
                WindowEvent::CloseRequested => {
                    //TODO: just close one window
                    elwt.exit();
                }
                _ => {}
            }
        })
        .unwrap();
}
